Biomarkers are needed to accurately predict short-term breast cancer risk, so that 1) women who are most likely to benefit from preventive therapy can be identified, and 2) response to chemoprevention can be accurately assessed. This proposal aims to characterize a signal-transduction pathway that we hypothesize plays an important role in targeting the elimination of acutely damaged mammary epithelial cells. In preclinical models, we observe that 1) the retinoic acid receptor-beta 2 (RARbeta2) and the CREB-binding protein, CBP, regulate proliferation and promote apoptosis in acutely damaged mammary epithelial cells, 2) RARbeta2 regulates the expression of CBP in a positive feedback loop, and 3) suppression of RARbeta2 or CBP inhibits apoptosis. Based on these observations we will test the hypothesis that 1) RARbeta2 and CBP promote apoptosis in acutely damaged HMECs through IRF-1-induction and 2) RARbeta2 P2 methylation predicts loss of CBP expression in mammary epithelial cells obtained from high-risk women. Specific Aim I will test whether RARbeta2 and CBP promote apoptosis in acutely damaged HMECs through recruitment to the IRF-1 promoter and indution of IRF-1. Specific Aim II will test whether the presence of RARbeta2 P2 promoter methylation predicts loss of CBP expression in mammary epithelial cell strains obtained from women at high-risk from breast cancer. Specific Aim III will use a research technique called Random Periareolar Fine Needle Aspirate (RPFNA) to test whether methylation inactivation of RARbeta2 in high-risk women promotes 1) loss of RARbeta2 and CBP expression and 2) predicts short-term cytological progression. The correlation between RARbeta2 P2 methylation and CBP expression in RPFNA will be tested by MS-PCR and quantitative RT-PCR in microdissected epithelial cell clusters. Cytological progression will be tested in high-risk women in our chemoprevention cohort. Relevance to public health: Information obtained in this proposal can be immediately used to 1) improve our ability to predict short-term breast cancer-risk and 2) develop makers to test whether women who are at high-risk for breast cancer are responding to prevention agents.